In this study, we consider the demagnetization of magnets due to reverse magnetic field current, in order to find out the cause of local demagnetization of concentrated winding IPMSMs operating in high-temperature environments. It is clarified that the demagnetization part acting on the magnet greatly differs depending on the energized phase. We propose a method for demagnetization evaluation based on 2-phase and 3-phase energization using a test rotor with only two adjacent poles of a multipolar rotor.